1. Field of the Invention
The present invention relates to an ATM exchange system and, more particularly, to an ADSL (Asymmetric Digital Subscriber Line) interfacing system in the ATM exchanger which is designed to interface ADSL subscribers with the ATM exchanger.
2. Description of the Related Art
High-speed transmission media are usually needed in order to be served with Internet or VOD (Video on Demand) service of high quality. This is the principal reason for appearance of ISDN (Integrated Services Digital Network) as a high-speed transmission medium.
The ISDN is an integrated services network that combines voice and non-voice services in the electrical communication network using the digital system, digitalizing non-voice information such as images and data as well as voice information to be connect with highly developed communication equipment or computers via subscribers lines. The ISDN has enabled efficient data transmission, storage and processing.
The effective service speed for exchanged or fixed connection ranges from 64 Kbps to 128 Kbps. The maximum rate of 128 Kbps can be served by use of optical cables to realize high-speed service and satisfy the request of subscribers.
However, there has remained a problem in that all cables between the telephone station and subscribers must be replaced with optical cables that are too expensive, in order to realize the high-speed services.
Accordingly, an object of the present invention is to provide high speed VOD or internet services for general subscribers with telephone lines by interfacing the subscribers connected to the ADSL interfacing system with an ATM exchanger.
To achieve these and other advantages, and in accordance with the purpose of the present invention as embodied and broadly described, an ADSL interfacing system of ATM exchanger includes: a CPU and peripheral circuit section for receiving signals from a subscriber terminal and identifying a specified value to be synchronized; an upstream cell processing section for converting the signals received from the subscriber terminal to an ATM cell to be transmitted to a subscriber control system; and a downstream cell processing section for converting the signals received from the subscriber control system to transmission signals to be sent to the subscriber terminal. The CPU and peripheral circuit section receives the signals from the subscriber terminal in the unit of bytes, and the downstream cell processing section converts the signals received from the subscriber control system to an E1 signal to be sent to the subscriber terminal.
Alternatively, in the ADSL interfacing system of ATM exchanger according to the preferred embodiment of the present invention, a cell testing buffer section is further included to output test cells received via the respective components of the upstream cell processing section to the downstream cell processing section, and local loop-back test cells received via the respective components of the downstream cell processing section to the CPU and peripheral circuit section.
Furthermore, the CPU and peripheral circuit section generates the test cells, applies them to the upstream cell processing section, reads out the local loop-back test cells via the cell testing buffer section, and compares the test cells and the local loop-back test cells in order to check the presence of errors.